Most commercially available magnetic recording media are an in-plane magnetic recording media where the magnetic easy axis of the magnetic film is mainly oriented parallel to the substrate. If such an in-plane magnetic recording medium is fabricated to have a high recording density, the bit volume is excessively reduced and the reproduction properties may deteriorate due to a thermal fluctuation effect or the like. Furthermore, it is also known that media with high recording density suffer from an increase in the medium noise due to expansion of the magnetization reversal transition region or the like.
On the other hand, a so-called vertical magnetic recording medium where the magnetic easy axis in the magnetic film is oriented perpendicularly to the substrate is advantageous in that low noise can be attained even with high recording density. This is because a sharp magnetization transition is formed and as the recording density increases, the demagnetization field is decreased and stabilized. Moreover, high recording density can be attained even when the bit volume is relatively large. As such, the vertical magnetic recording medium is drawing the attention of investigators in this field.
However, the vertical magnetic recording medium has a reproduction waveform different from that of the in-plane magnetic recording medium. More specifically, the isolated waveform is not a single peak type but contains a di-pulse waveform. Accordingly, it is difficult to apply the signal processing system commonly used for in-plane recording media without modification.
To cope with this, a vertical and in-plane composite type magnetic recording medium has been proposed, which comprises both an in-plain magnetic film and a vertical magnetic film. Such structure enables the use of the same signal processing system as used for in-plane magnetic recording media.
In recent years, the demand for magnetic recording media with higher recording density has been increasing and in keeping with this tendency, there is a demand for improved noise properties.
However, conventional magnetic recording media are by no means entirely satisfactory with respect to noise properties, and there is also a demand for magnetic recording media having more excellent noise properties. The present invention has been achieved in consideration of the above problems of the prior art.